Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating types of vascular disease. In particular, angioplasty is widely used for opening stenoses in the coronary arteries and is used for treating stenoses in other vascular regions.
One widely used form of angioplasty makes use of a dilatation catheter which has a inflatable balloon at the distal end and a guide wire lumen within at least a portion of the catheter shaft. Typically, a guide wire is inserted through the vascular system to a position near the stenoses, leaving a proximal portion of the guide wire extending from the patient. The proximal guide wire portion is threaded through the dilatation catheter guide wire lumen and the dilatation catheter advanced through the vascular system over the guide wire to the position near the stenoses. The treating physician manipulates the dilatation catheter until the balloon is positioned across the stenoses. The balloon is then inflated by supplying fluid under pressure through an inflation lumen in the catheter to the balloon. The inflation of the balloon widens the lumen through the stenosed area by pressing the inflating balloon wall against the lesion inside wall.
Current angioplasty catheters often have a short strain relief surrounding a hypotube segment that forms the proximal shaft of the catheter. Hypotube, or thin-walled hypodermic tubing, has many desirable characteristics, but can kink if bent too sharply. Strain reliefs are commonly formed of a polymeric material extending distally from a manifold affixed to the proximal end of a catheter shaft. The current designs can inhibit kinking where the hypotube exits the manifold within the strain relief. Existing strain reliefs commonly have a length of about 1 to 2 inches. Some catheters are returned by users, having kinked proximal shaft regions in spite of the existing strain reliefs. Applicants believe catheter proximal shaft designs could be improved to further reduce kinking.
Catheters have flexibility requirements that vary with the location along the catheter length. Less flexibility may be required in the catheter proximal portion, where the catheter may lie within a large inside diameter, straight vessel portion. Greater flexibility is often a design goal in the catheter distal portion, where traversing small inside diameter, tortuous vessels may be required. In the catheter mid-region, a gradually, distally increasing flexibility is desirable rather than an abrupt change from low to high flexibility. What would be desirable is a catheter including a mid-region having a distally increasing flexibility while retaining the advantages of hypotube.
Present catheters having hypotube proximal shafts have the advantages of hypotube and one disadvantage of hypotube, that of sometimes excessive springiness. In use, current catheters can exhibit a large amount of spring or whipping about of the unconstrained portion. This can make handling the catheter somewhat difficult in the operating room. What would be desirable is a catheter having the advantages of a proximal hypotube portion but without the spring of current hypotube shafts.